aboutsummaryrefslogtreecommitdiff
path: root/internal/bufpool
diff options
context:
space:
mode:
authorGravatar Runxi Yu2026-02-20 19:06:13 +0800
committerGravatar Runxi Yu2026-02-20 19:07:14 +0800
commitaa513c069c1418734aea894dc944e27c6a78a3bb (patch)
tree687f0a11bb550fa088fd82a98ceb8979bbc35f69 /internal/bufpool
parentComment on prior reverts removing the pack writing API (diff)
signatureNo signature
Delete everything, I'm redesigning this.
I'll stop using a flat package and make things much more modular. And also experiment with streaming APIs so large blobs don't OOM us.
Diffstat (limited to 'internal/bufpool')
-rw-r--r--internal/bufpool/buffers.go189
-rw-r--r--internal/bufpool/buffers_test.go77
2 files changed, 0 insertions, 266 deletions
diff --git a/internal/bufpool/buffers.go b/internal/bufpool/buffers.go
deleted file mode 100644
index 439e7e04..00000000
--- a/internal/bufpool/buffers.go
+++ /dev/null
@@ -1,189 +0,0 @@
-// Package bufpool provides a lightweight byte-buffer type with optional
-// pooling.
-package bufpool
-
-import "sync"
-
-const (
- // DefaultBufferCap is the minimum capacity a borrowed buffer will have.
- // Borrow() will allocate or retrieve a buffer with at least this capacity.
- DefaultBufferCap = 32 * 1024
-
- // maxPooledBuffer defines the maximum capacity of a buffer that may be
- // returned to the pool. Buffers larger than this will not be pooled to
- // avoid unbounded memory usage.
- maxPooledBuffer = 8 << 20
-)
-
-// Buffer is a growable byte container that optionally participates in a
-// memory pool. A Buffer may be obtained through Borrow() or constructed
-// directly from owned data via FromOwned().
-//
-// A Buffer's underlying slice may grow as needed. When finished with a
-// pooled buffer, the caller should invoke Release() to return it to the pool.
-//
-// Buffers must not be copied after first use; doing so can cause double-returns
-// to the pool and data races.
-//
-//go:nocopy
-type Buffer struct {
- _ struct{} // for nocopy
- buf []byte
- pool poolIndex
-}
-
-type poolIndex int8
-
-const (
- unpooled poolIndex = -1
-)
-
-var sizeClasses = [...]int{
- DefaultBufferCap,
- 64 << 10,
- 128 << 10,
- 256 << 10,
- 512 << 10,
- 1 << 20,
- 2 << 20,
- 4 << 20,
- maxPooledBuffer,
-}
-
-var bufferPools = func() []sync.Pool {
- pools := make([]sync.Pool, len(sizeClasses))
- for i, classCap := range sizeClasses {
- capCopy := classCap
- pools[i].New = func() any {
- buf := make([]byte, 0, capCopy)
- return &buf
- }
- }
- return pools
-}()
-
-// Borrow retrieves a Buffer suitable for storing up to capHint bytes.
-// The returned Buffer may come from an internal sync.Pool.
-//
-// If capHint is smaller than DefaultBufferCap, it is automatically raised
-// to DefaultBufferCap. If no pooled buffer has sufficient capacity, a new
-// unpooled buffer is allocated.
-//
-// The caller must call Release() when finished using the returned Buffer.
-func Borrow(capHint int) Buffer {
- if capHint < DefaultBufferCap {
- capHint = DefaultBufferCap
- }
- classIdx, classCap, pooled := classFor(capHint)
- if !pooled {
- newBuf := make([]byte, 0, capHint)
- return Buffer{buf: newBuf, pool: unpooled}
- }
- buf := bufferPools[classIdx].Get().(*[]byte)
- if cap(*buf) < classCap {
- *buf = make([]byte, 0, classCap)
- }
- slice := (*buf)[:0]
- return Buffer{buf: slice, pool: poolIndex(classIdx)}
-}
-
-// FromOwned constructs a Buffer from a caller-owned byte slice. The resulting
-// Buffer does not participate in pooling and will never be returned to the
-// internal pool when released.
-func FromOwned(buf []byte) Buffer {
- return Buffer{buf: buf, pool: unpooled}
-}
-
-// Resize adjusts the length of the buffer to n bytes. If n exceeds the current
-// capacity, the underlying storage is grown. If n is negative, it is treated
-// as zero.
-//
-// The buffer's new contents beyond the previous length are undefined.
-func (buf *Buffer) Resize(n int) {
- if n < 0 {
- n = 0
- }
- buf.ensureCapacity(n)
- buf.buf = buf.buf[:n]
-}
-
-// Append copies the provided bytes onto the end of the buffer, growing its
-// capacity if required. If src is empty, the method does nothing.
-//
-// The receiver retains ownership of the data; the caller may reuse src freely.
-func (buf *Buffer) Append(src []byte) {
- if len(src) == 0 {
- return
- }
- start := len(buf.buf)
- buf.ensureCapacity(start + len(src))
- buf.buf = buf.buf[:start+len(src)]
- copy(buf.buf[start:], src)
-}
-
-// Bytes returns the underlying byte slice that represents the current contents
-// of the buffer. Modifying the returned slice modifies the Buffer itself.
-func (buf *Buffer) Bytes() []byte {
- return buf.buf
-}
-
-// Release returns the buffer to the global pool if it originated from the
-// pool and its capacity is no larger than maxPooledBuffer. After release, the
-// Buffer becomes invalid and should not be used further.
-//
-// Releasing a non-pooled buffer has no effect beyond clearing its internal
-// storage.
-func (buf *Buffer) Release() {
- if buf.buf == nil {
- return
- }
- buf.returnToPool()
- buf.buf = nil
- buf.pool = unpooled
-}
-
-// ensureCapacity grows the underlying buffer to accommodate the requested
-// number of bytes. Growth doubles the capacity by default unless a larger
-// expansion is needed. If the previous storage was pooled and not oversized,
-// it is returned to the pool.
-func (buf *Buffer) ensureCapacity(needed int) {
- if cap(buf.buf) >= needed {
- return
- }
- classIdx, classCap, pooled := classFor(needed)
- var newBuf []byte
- if pooled {
- raw := bufferPools[classIdx].Get().(*[]byte)
- if cap(*raw) < classCap {
- *raw = make([]byte, 0, classCap)
- }
- newBuf = (*raw)[:len(buf.buf)]
- } else {
- newBuf = make([]byte, len(buf.buf), classCap)
- }
- copy(newBuf, buf.buf)
- buf.returnToPool()
- buf.buf = newBuf
- if pooled {
- buf.pool = poolIndex(classIdx)
- } else {
- buf.pool = unpooled
- }
-}
-
-func classFor(size int) (idx int, classCap int, ok bool) {
- for i, class := range sizeClasses {
- if size <= class {
- return i, class, true
- }
- }
- return -1, size, false
-}
-
-func (buf *Buffer) returnToPool() {
- if buf.pool == unpooled {
- return
- }
- tmp := buf.buf[:0]
- bufferPools[int(buf.pool)].Put(&tmp)
-}
diff --git a/internal/bufpool/buffers_test.go b/internal/bufpool/buffers_test.go
deleted file mode 100644
index f5c006da..00000000
--- a/internal/bufpool/buffers_test.go
+++ /dev/null
@@ -1,77 +0,0 @@
-package bufpool
-
-import "testing"
-
-func TestBorrowBufferResizeAndAppend(t *testing.T) {
- b := Borrow(1)
- defer b.Release()
-
- if cap(b.buf) < DefaultBufferCap {
- t.Fatalf("expected capacity >= %d, got %d", DefaultBufferCap, cap(b.buf))
- }
-
- b.Append([]byte("alpha"))
- b.Append([]byte("beta"))
- if got := string(b.Bytes()); got != "alphabeta" {
- t.Fatalf("unexpected contents: %q", got)
- }
-
- b.Resize(3)
- if got := string(b.Bytes()); got != "alp" {
- t.Fatalf("resize shrink mismatch: %q", got)
- }
-
- b.Resize(8)
- if len(b.Bytes()) != 8 {
- t.Fatalf("expected len 8 after grow, got %d", len(b.Bytes()))
- }
- if prefix := string(b.Bytes()[:3]); prefix != "alp" {
- t.Fatalf("prefix lost after grow: %q", prefix)
- }
-}
-
-func TestBorrowBufferRelease(t *testing.T) {
- b := Borrow(DefaultBufferCap / 2)
- b.Append([]byte("data"))
- b.Release()
- if b.buf != nil {
- t.Fatal("expected buffer cleared after release")
- }
-}
-
-func TestBorrowUsesLargerPools(t *testing.T) {
- const request = DefaultBufferCap * 4
-
- classIdx, classCap, pooled := classFor(request)
- if !pooled {
- t.Fatalf("expected %d to map to a pooled class", request)
- }
-
- b := Borrow(request)
- if b.pool != poolIndex(classIdx) {
- t.Fatalf("expected pooled buffer in class %d, got %d", classIdx, b.pool)
- }
- if cap(b.buf) != classCap {
- t.Fatalf("expected capacity %d, got %d", classCap, cap(b.buf))
- }
- b.Release()
-
- b2 := Borrow(request)
- defer b2.Release()
- if b2.pool != poolIndex(classIdx) {
- t.Fatalf("expected pooled buffer in class %d on reuse, got %d", classIdx, b2.pool)
- }
- if cap(b2.buf) != classCap {
- t.Fatalf("expected capacity %d on reuse, got %d", classCap, cap(b2.buf))
- }
-}
-
-func TestGrowingBufferStaysPooled(t *testing.T) {
- b := Borrow(DefaultBufferCap)
- defer b.Release()
-
- b.Append(make([]byte, DefaultBufferCap*3))
- if b.pool == unpooled {
- t.Fatal("buffer should stay pooled after growth within limit")
- }
-}